Electromagnetic switch.



E. J. MURPHY.

ELECTROMAGNETIC SWITCH.

APPLICATION FILED JULY 13. 1914."

1,231,1E12. Patented June 26, 1917.

Fig. l. v Fig. 2.

INT/ENTER EDI/WM J MURPHZ STATES PATENT ormon.

'nnwnr J. nunrnr, or SOHENECTADY, new roan, nssrcnon 'ro GENERALntncrnre comm, A CORPORATION or new YORK.

Specification of Letters Patent.

ELECTROMAGNETIC SWITCH.

Patented June 26, 1917.

Application filed July 13, 1914. Serial No. 850,596.

To all whom it may oonaem: Be it known that I, Enwm J. Munrmr, a citizenof the United' States, residing at Schenectad in the county ofSchenectady, State of ew York, have invented certain new and usefulImprovements in Electro-.

magnetic Switches, is a specification.

This invention relates to electromagnetic switches and has for itsobject the provision of a device of this character in which the contactscannot stick or freeze together under the most trying conditions ofservice and at the same time are spring pressed apart at all times. I

In the operation of electromagnetic switches, especially as. used in thecontrol of of which the following electric motors where the switches,are opery ated very frequently and the currents are heavy, .it sometimeshappens that the are formed between the contacts fuses the metal andcauses the contacts to stick together, due to the formation of a slightweld between them. This most fre uently happens when the magnetizing winingl is not energlzed -long enough to cause t e contacts to be broughtfirmly into engagement with each other in their final position, but isonly energized for an instant so that the contacts 80 just touch andthen separate. This also happens sometimes because of the slow openingof the contacts due to slow decrease of magnetic pull and other causes.In the type of contact for electromagnetic switches now well known, inwhich the contacts slide or roll upon each other to produce a wipingaction, any slight welding or sticking will be overcome by the wipingaction if the contacts are closed or wiped home. If, however, thecontacts merely engage or kiss without being wiped to the finalposition, a weld might form which would hold the contacts in the closedposition against the tendency of gravity or the spring to open theswitch. One of the objects of my invention is to overcome thisdifficulty and make it practically impossible for the. contacts ofv theswitch to stick together in the manner above described.

Another object of my invention is to provide a switch which is springpressed to the open position as distinguished from being biased to theopen position by gravity. It is frequently desirable that the contactorshould be capable of being tilted at an angle say of 45 or more withoutdanger of the fO I'IIL 'TTTh B arrangement is such that closes.

the contacts so that contacts dropping closed. On shipboard forinstance, a'cohtactor must be arrange so that the'eonta'cts cannotpossibl drop closed under the worst conditions of rollmg-and copitching. One of the inherent difliculties in making a switchof thiskind with spring opened contacts is thatif the spring is strongenough tobe of any advantage in causlnga-strong pressure betweenthe contacts inclosed position, it will be so strong that the magnet cannot move itfrom the open position. As the contactor approaches closed position, theclosing force Increases very rapidly, but in the open position theforce-is relatively weak and it is therefore the open position.

carry ng out my invention, 1 provide a switch. WhICll is'spring pressedto the open necessary that the spring should be-weak in position, thecontacts being forced apart near the'closed position with sufiicientforce to break any weld which might possibly the effective pressuretending to hold the eontacts apart is less when the switch is in theopen position than it is just before the switch This is accomplished bydecreasing the leverage at which the magnet acts upon the spring justprior to the engagement of 8-5 the effective pressure tending to holdthe contacts open will be considerably increased. From this point onuntil the contacts reach their final position, there is a strong springpressure between the contacts so that any weld which might form betweenthe contacts will be instantly broken, and while it might be possiblethat the contacts would be brought into engagement with each other insuch a way as to form a weld, this weld would be immediately broken bythe strong spring pressure which acts over a suflicient ran e to breakany weld which could form. Other objects and purposes of my inventionwill appear in the course of the following specification in which I haveshown my invention embodied in concrete form for purposes ofillustration.

In the accompanying drawing, Figure 1 represents a side view of anelectromagnetic c'arryihg member 17and' presses. the latter against thesto'pli19. ,This spring engages the member, 17 between the' pivot andthe" stop,'and thepoint of engagement s 1mport'ant because it afiects.the leverage at pivot pin 18. on thearmature of course moves withthearmaturc, but the spring 20 forces the lower end of the member 17againstv the stop 19. The effective action of the spring 20 tending tomove the contacts apart is therefore due to ,acomp'ound lever age.Representing the distance between the pivot pin 18 and the stop19'by a,and the distance between the spring and the stop 19 by b, and thedistance between the pivot pin ltand the pivot pin-18 by-c, then theefiective action of the spring tending to hold the contacts apart isdueto the force of the spring acting at the distance OX2- The.

nearer the spring is located to the stop 19 the less Wlll betheefiectivejl'everage at which the spring-acts and hence the lesseifective force there will be to hold the armature in the open position.When the armature moves inward, the member 17 slides and rolls on thestop 19 and a relatively large movement of the member 13' compresses thespring a relativelysmall amount. This will be seen by reference to Fig.4. In this figure the switch has reached the position in which theeffective pressure of the spring tending to open the contacts isincreased.- This is brought about by the engagement of 'the lower end ofthe member 17 with the shoulder 21. From this point on in the movementof the switch arm it will be seen that the spring will act directly uponthe armature member since the member 17 now moves as a unit with themember 13. Relatively small movement of the armature to closed positionnow compresses the spring a relatively large amount. When the contacts15 and 16 engage, they wipe or roll on each other and the member 17 is's'shown in the.

would tend to cause the contacts to stick ,together'will be overcome bythe spring ten- "screw 23 which slides in the slot 23'. The

contact carrying member is made in the acts against each leg of theyoke. A bar 25 secured to the armature member corresponds with theshoulder 21,-Figs. 3 to 5:

form of a yoke 24 so that oneof the springs andkprojects beyond, thearmature member at each end so asto be engaged by the legs of thecontact carrying member. A plate 26 is secured in a stationary positionby means of a rod 27 which is secured in the frame of the magnet andpasses through a Nuts 28 on this rod secure the plate in place.

Screws 19 ,form stops corresponding to the stop 19 in Fig. 3.The'operation and general arrangement of parts is identical with thatalreadydescribed in connection clearance hole in the armature member.

with Figs. 3and 5 and no further 'description is therefore. deemednecessary.

It will be seen that the electromagnetic switch above described isspring pressed to the open position but the force necessary to move theswitch from, the open position to the intermediate position shown inFig. 4 is relatively small as compared with the force necessary to moveit the remainder of the distance. This makes a very strong pressurebetween the contacts for a short distance, enough to break any weldwhich might form, and produce a good spring pressure on the movablecontact in the closed position. On the other hand, in the open position,the spring is weak enough so that it can be readily moved over the wideair gap which then exists. While I have desince various modificationsthereof will suggest themselves to those skilled in the art withoutdeparting from the spirit of my invention, the scope of which is setforth in the annexed claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is

1. An electromagnetic switch comprising a magnetizing winding, a fixedcontact, a pivoted armature member having a contact mounted thereon andspring pressed away from the-fixed contact so as to have a resilientmovement with reference to the armature member, and means whereby theleverage at which the spring acts upon the armature member tending tokeep the contacts apart is decreased before the movable contact reachesits closed position.

2. An electromagnetic switch comprising a magnetizing winding, a fixedcontact, an armature member, a contact having a resilient mountingthereon to permit a yielding movement with reference to the armaturemember and press the armature member toward open position, and meanswhereby the effective pressure tending to hold the contacts apart isincreased when the armature member reaches a predetermined position inthe closing. movement. I

3. An electromagnetic switch comprising a magnetizing winding, a fixedcontact, an armature member having a contact movably mounted thereon,and spring pressed away from the fixed contact, and means whereby thespring pressure tending to hold the con tacts open is substantiallyuniform during the closing movement until the armature member reaches apredetermined position and is then increased.

4. An electromagnetic switch comprising a magnetizing winding, a fixedcontact, an armature member having a contact pivoted thereon tocooperate with the fixed contact,

a spring interposed between the pivoted contact and a stationary part ofthe switch so that the contacts will be held apart thereby and engagewith a yielding pressure, and means whereby the effective pressuretending to hold the contacts apart is increased when the armature memberreaches a predetermined position in the closing movement.

5. An electromagnetic switch comprising a magnetizing winding, a fixedcontact, an armature member, a contact pivoted on said armature niemberto cooperate with said fixed contact, a spring interposed between astationary portion of the switch and said pivoted contact tending toturnthe latter on its pivot toward the xed contact, a fixed stop againstwhich the contact ispressed by the spring, and a stop on the armaturemember which engages the pivoted contact at'a predetermined position 1nthe closing movement so that further movement of the armature membermoves the pivoted contact away from the fixed stop.

6. An electromagnetic switch comprising a magnetizing winding, a fixedcontact, an armature, a contact carrying member pivoted thereto, a fixedstop in the path of said contact member to prevent it from rotating in adirection to cause engagement of the contacts, a spring mounted to pressthe member against the stop and bias the armature to open position, anda stop on the armature which engages the pivoted contact member at apredetermined position in the closing movement so that further movementof the armature moves the contact member away from the fixed stop.

7. An electromagnetic switch comprising a magnetizing winding, a fixedcontact, an armature, a contact carrying member pivoted thereto, a stopon the armature which limits the rotation of the contact member on itspivot in a'direction to engage the fixed contact, a spring engaging saidmember between the pivot and the stop and tending to force it againstthe latter, and a fixed stop between the spring and the stop on thearmature which acts as a fulcrum for the contact carrying member incompressing the spring during the closing movement until the contactcarrying member engages the stop on the armature and is moved away fromthe fixed stop.

8. An electromagnetic switch comprising a magnetizing winding, a fixedcontact, an armature member having a contact pivotally mounted thereon,and spring pressed away from the fixed contact so that there will be ayielding pressure between the contacts when they engage, and meanswhereby the spring pressure tending to hold the contacts open issubstantially uniform during the ,closing movement until the armaturemember reaches a predetermined position and is then increased. 7

9. An electromagnetic switch comprising a magnetizing winding, a fixedcontact, an armature member, a contact having a resilient mounting whichpermits yielding move ment with reference to the armature member andforces the contact away from the fixed contact, and means whereby thepressure tending to hold the contacts apart is substantially uniformduring the closing movement until the armature member reaches apredetermined position and is then increased.

In witness whereof, I have hereunto set my hand this 11th day of July,1914.

EDWIN J. MURPHY. Witnesses:

HELE ORFORD, MARGARET E. WOOLLEY.

